Manufacture of nickel iron alloys



Patented Sept. 20, 1932- I UNITED STATES PATIENT OFFICE GEORGE CHRISTODHEB HARRIS, 01 LONDON, GEO'FFBEY RICHARD POLGBEEN, OI

. WEMBLEY, AND STANLEY VAUGHAN WILLIAHS, OF KENTON, ENGLAND nmurao'rm or moxnnmox annoys Ho Drawing. Application med December-i6, 1880, Serial Ho. 502,848, and in Grta't Britain January 2!, 1880.

This invention relates to the manufacture of nickel iron alloys in the form of powder, the object of the invention being the production of such powdered alloys in an improved I manner whereby the alloyed powder produced has a particle-size distribution and other physical properties which render it suitable for the manufacture of cores for loading coils, electromagnets or the like.

A process for the production of nickel-iron powders is already known wherein the mixed oxides of the metals are reduced in a stream,

of gas. We have found that it. is not easy a by that process to obtain the alloy in a suitable physical state. If the reduction temperature is low, the metals do not alloy sufciently rapidly; ifit is high, though the alloying is complete, the grain size of the resulting powder is too large, and the par- 20 ticles are not easily broken up. We have found further that this difiiculty can be removed by reducing at a low temperature and heating the reduced powder for a suitable time to a higher temperature, especially if the reduced powder is washed before being raised to the higher temperature. The heating of the powder at the higher temperature generally results in the formation of a coherent block; it will therefore be termed here sintering; but it must be understood that the aggregation of the particles is not an essential element of the process, and that the beneficial results of the second heating, which we term sintering, may be obtained when the material remalns a powder.

According to the first feature of the invention the manufacture of alloy powders containing nickel and iron by the reduction of the mixed oxides of the metals in a stream of gas comprises the sintering of the reduced powder at a temperature higher than that of reduction, whereby alloying is completed and a favourable size and physical character of the particles is produced. Preferably the reduced powder is washed in. water or a dilute acid (for example dilute hydrochloric acid) after reduction and before sintering. If the particles of the reduced powder are already slightly sintered together, they should be broken up before was ing.

ing with a suita le quantity of a fine refractory powder. Preferably this refractory owder is mixed with the metal powder durng the powdering of the metal after sintermg. Talc is a suitable refractory powder.

Thus, in an example of one method of carrylng out the process in accordance with the invention, suitable weights of nickel and iron oxides in powder form and in such proport1 ons as to give the desired proportions of nickel and H011 in the resulting alloy, are mlxed together. The powders are mixed either in the dry condition by means of a mechanical mixer, or may be mixed in a wet condition by means of a mechanical mixer, or may be mixed in a wet condition by means of acolloid mill. is adopted the suspension is filtered after mixing and is then dried.

The mixed oxides are now reduced in a current of h drogen at a suitable tempera- If the latter alternative ture, (850 or example). The roduct of reduction may now be in a slight sintered condition, but can be readily bro en down to a fine powder in a rotary pulverizer.

The fine product is now washed with a five per cent hydrochloric acid solution at 50 0., one litre of solution being allowed for each kilogram of alloy. The acid is next decanted,

and the powder is washed thoroughlywith cold water and dried in an oven.

.The washed powder is now sintered by ried out at a higher temperature,'and vice versa. The metal owder is now mixed with about 2 70 of ne talc powder and annealed. If the metal is a 80: nickel iron alloy, it may be annealed at about900 C. It is then provided with a suitable insulating coating and ressed into cores. The coating may suita lybe produced by heating the powder in a solution of chromic anhydride and a halogen acid or halogen salt, the heating being continued until the solution has evaporated substantially to dryness.

The process in accordance with the inven- 'tion may conveniently be applied to magnetic alloys containing nickel, iron and cobalt, such as t e known ternary alloys in which these elements are used to give the required mag- 'netic qualities, low hysteresis loss, for :ex-

ample.

a What we claim is 1. A process for the manufacture of alloy powders containing nickel and iron, which comprises mixing the powdered oxides (of nickel and iron, reducing the mixture by heating in a reducing gas, washing the product, drying the product, and sintering the product at a temperature higher than the temperature used for the reduction of the -mixture.

2- A process for the manufacture of alloy powders containing nickel and iron, which comprises mixing the powdered oxides of i nickel and iron, reducing the mixture by heating in a reducing gas, washing the product, drying and sintering the product at a temperature higher thanthe temperature used the product at a powders containing .nickel, iron and cobalt. whichcomprises mixing the powdered oxides of nickel, iron and cobalt, reducing the mixture by heating in a reducinggas, washing the product, drying and sintering the prodnot at a temperature higher than the temperature used for reducing the mixed oxides.

7. Cores for loading coils and electromag nets comprising a nickel iron alloy pressed from powdered alloy obtained by reducing a mixture containing nickel oxide and iron oxide byheating in a reducing gas, sintering the product at a temperature higher than that used for the reduction, pulverizing the sintered alloy and coating the alloyparticles with an insulating coating.

v GEORGE CHRISTOPHER MARRIS.

crorraer RICHARD POLGREEN.

STANLEY VAUGHAN WILLIAMS;

for the reduction of the mixture, and then 5 subjecting the mixture to pulverization.

.3. A process for the manufacture of alloy powders containingnickel and iron, which comprises mixingthe powdered oxides of -nickel and iron, reducing the mixture b not, drying and sintering temperature higher than the a temperature heating ina reducing gas, washing the pro the product at a used for the reduction of the mixture, pulyerizing the product, mixing the pulverized .product with a refractorypowder and annealing theresultant mixture.

4. A process for the manufacture of alloy powders containing nickel and iron, which comprises mixing the powdered oxides of nickel and iron, reduclng the mixture b heating in a reducing gas,washingthe pro uc't, drying and sintering the product at a tem erature higher than the temperature the temperature v washing the prodthen coating the use for the reduction-of the mixture, pulverizingj the product,mixing the pulverized product with powdered talc, and annealing the resultant mixture.

'- 5. A process for the manufacture of alloy powders containingnickel and iron, which,

comprises mixing the powdered oxides of nickel and iron, reducing the mixture by 

